A spinal cord injury occurs when trauma or disease damages the spinal cord and results in partial or complete paralysis. The level of paralysis is determined by where the damage occurs, i.e. in the neck or in the back. Besides paralysis there are usually signs of sensory loss, incontinence, intractable pain and pressure sores. The world-wide annual incidence of SCI has been estimated to be around 22 per million with approximately 2.5 million survivors living with SCI induced paralysis. As today, there is no therapy which restores or even significantly improves the spinal cord function in those severe cases.
Attempts to use peripheral nerve grafts for bridging spinal cord gaps in rats was reported by Cheng et al in 1996 (Science, 273: 510). The nerve grafts redirected descending motor pathways from cranial (proximal) non-permissive white matter to caudal (distal) permissive gray matter and ascending pathways from caudal white to cranial gray matter. FGF1 was added to decrease gliosis and enhance axon regeneration. The nerve grafts were positioned in the gap between the two spinal cord ends and kept in the right position by tissue glue. Animals subjected to the repair procedure, i.e. implantation of nerve grafts together with FGF1, significantly improved in their hind limb function. The first improvements were observed a few weeks after surgery and continued through one year of observation. Attempts to further improve the spinal cord repair procedures have been made by using magnetic resonance imaging (MRI) to assess the lesion extent before surgery, see Fraidakis et al (Experimental Neurology 188(2004)33-42). Thin serial MRI sections allowed identification of gray and white matter and visualization of cyst formation. After resecting the lesioned spinal cord, as necessary, autologous intercostal nerve grafts were implanted and the repair site was embedded in fibrin glue containing acidic FGF.
Preformed devices for bridging a gap in a spinal cord and methods for manufacture thereof, are also known from prior art, see e.g. U.S. Pat. No. 6,235,041 (Cheng and Olsson), U.S. Pat. No. 7,163,545 (Yaszemski et al) and WO 2007/111562 (Svensson and Mattsson). General designs are disclosed, but there is no teaching of devices adopted for the level, size and shape of the spinal cord injury.
However, in spite of considerable time from early disclosures of the basic principle of connecting the routing of tracts in white to gray matter, the translation into a clinically applicable method has been absent. Still, no product is available on the market. The spinal cord is an extremely important part of the central nervous system, where a patient with a complete injury faces a permanent loss of function below the site of injury, with devastating consequences for the patient's quality of life, as well as long-term costs to finance the assistance to the patient. In many cases the patient is a fairly young person who has been involved in a serious accident and will have to spend the rest of life with no chance for functional improvements.